package com.mvp.lt.airlineview.kml.utils;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;

/**
 * Created by ${LiuTao}.
 * User: Administrator
 * Name: AirLineView
 * functiona:
 * Date: 2019/7/2 0002
 * Time: 上午 11:13
 */
public class UnicodeInputStream {
    PushbackInputStream internalIn;
    boolean isInited = false;
    String defaultEnc;
    String encoding;

    private static final int BOM_SIZE = 4;

    public UnicodeInputStream(InputStream in, String defaultEnc) {
        internalIn = new PushbackInputStream(in, BOM_SIZE);
        this.defaultEnc = defaultEnc;
    }

    public String getDefaultEncoding() {
        return defaultEnc;
    }

    public String getEncoding() {
        if (!isInited) {
            try {
                init();
            } catch (IOException ex) {
                IllegalStateException ise = new IllegalStateException(
                        "Init method failed.");
                ise.initCause(ise);
                throw ise;
            }
        }
        return encoding;
    }

    /**
     * Read-ahead four bytes and check for BOM marks. Extra bytes are unread
     * back to the stream, only BOM bytes are skipped.
     */
    protected void init() throws IOException {
        if (isInited)
            return;

        byte bom[] = new byte[BOM_SIZE];
        int n, unread;
        n = internalIn.read(bom, 0, bom.length);

        if ((bom[0] == (byte) 0x00) && (bom[1] == (byte) 0x00)
                && (bom[2] == (byte) 0xFE) && (bom[3] == (byte) 0xFF)) {
            encoding = "UTF-32BE";
            unread = n - 4;
        } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)
                && (bom[2] == (byte) 0x00) && (bom[3] == (byte) 0x00)) {
            encoding = "UTF-32LE";
            unread = n - 4;
        } else if ((bom[0] == (byte) 0xEF) && (bom[1] == (byte) 0xBB)
                && (bom[2] == (byte) 0xBF)) {
            encoding = "UTF-8";
            unread = n - 3;
        } else if ((bom[0] == (byte) 0xFE) && (bom[1] == (byte) 0xFF)) {
            encoding = "UTF-16BE";
            unread = n - 2;
        } else if ((bom[0] == (byte) 0xFF) && (bom[1] == (byte) 0xFE)) {
            encoding = "UTF-16LE";
            unread = n - 2;
        } else {
            // Unicode BOM mark not found, unread all bytes
            encoding = defaultEnc;
            unread = n;
        }
        // System.out.println("read=" + n + ", unread=" + unread);

        if (unread > 0)
            internalIn.unread(bom, (n - unread), unread);

        isInited = true;
    }

    public void close() throws IOException {
        // init();
        isInited = true;
        internalIn.close();
    }

    public int read() throws IOException {
        // init();
        isInited = true;
        return internalIn.read();
    }
}
